The present invention relates to a passive cooling system. More particularly, the invention relates to a solid state passive cooling system for cooling an enclosure sheltering heat-producing equipment such as, for example, a microwave repeater station.
Heat-producing equipment such as, for example, remote microwave repeater stations, are frequently subjected to very high ambient temperatures which may have a severe adverse affect on the life, reliability and performance of the equipment. Accordingly, conventional air conditioners have been used heretofore to reduce the temperature of the equipment enclosure below the maximum specified by the equipment manufacturer. The maximum specified temperature is typically 104.degree. F. or 40.degree. C.
A disadvantage of conventional air conditioners, however, is that they consume large amounts of electrical energy, from 800 to 1,500 watts, which energy is produced by large engine generator sets. The power required to run a conventional air conditioner is generally two or three times higher than the power required for the equipment. Thus, considerably larger volumes of expensive fuel are consumed in producing the energy than would be required with the passive cooling system of the invention.
Several passive cooling systems are currently being used to solve the aforedescribed problem. However, these systems utilize very large inside and outside heat exchangers as well as very large thermal storage tanks, since water or a water base solution is used as the thermal storage medium. The water base passive system is so inefficient in thermal storage and thermal transfer characteristics, operating on the thermosiphon process, that the prior art passive cooling systems are almost as large as the equipment enclosure itself. Furthermore, the passive cooling systems of the prior art are limited to desert applications, where nighttime temperatures drop sufficiently to permit the thermal storage water base solution to drop sufficiently in temperature to permit cooling during the following daytime period.
Passive cooling systems are described in a paper entitled "Standard Long-Range Operating Stations in Shelters With Integrated Thermal-Syphon System" by Franz Schmalzl of Siemens AG, Munich, Germany, presented at the 1979 International Telecommunications Energy Conference and appearing in the proceedings, 79CH1502-4, a brochure of Siemens Aktiengesellschaft, describing "Standard Long-Range Operating Station In Shelter Design With Integrated Systems For Temperature Control And Primary Power Sources", a Data Sheet of Ormat Systems Inc., N. S. Christopher, Inventor, for "Desert Microwave Repeater Cooling System", Technical Bulletin No. 052 of Ormat Systems Inc., March 1979, N. S. Christopher, Inventor, for "The Ormat Energy Converter and High Reliability Temperature Conditioning Equipment for Typical Telecommunications Systems Applications", Technical Bulletin No. 142 of Ormat Systems Inc., December 1979, for "Ormat Passive Cooling System for Radio Equipment Shelter" and Technical Bulletin No. 133 of Ormat Systems, Inc., for "Microwave Repeater Cooling Systems".
The cost of manufacture of the prior art passive cooling systems is very high, because they require large tanks and large heat exchangers, as well as large volumes of water base solutions which are difficult to transport to remote sites.
The principal object of the invention is to provide a passive cooling system which functions efficiently, effectively, reliably and economically to maintain a cool environment for enclosed heat-producing equipment.
An object of the invention is to provide a passive cooling system which functions efficiently, effectively and reliably to cool enclosed heat-producing equipment without consuming energy, except under extreme conditions.
Another object of the invention is to provide a passive cooling system which utilizes only solid state components and has no moving parts.
Still another object of the invention is to provide a passive cooling system of considerably smaller dimensions than known systems for cooling enclosed heat-producing equipment.
Yet another object of the invention is to provide a passive cooling system of simple structure, which is inexpensive in manufacture and operation, and functions efficiently, effectively and reliably to maintain a cool environment for enclosed heat-producing equipment.
An object of the invention is to provide a passive cooling system having considerably smaller dimensions and being considerably more aesthetically attractive than known systems for cooling enclosed heat-producing equipment, and being of simpler structure and less expensive in manufacture than such known systems.
Another object of the invention is to provide a passive cooling system which maintains a cooler environment for enclosed heat-producing equipment than known water storage cooling systems.
Still another object of the invention is to provide a passive cooling system which functions more efficiently and effectively, is of smaller size and dimensions and is less expensive in manufacture and operation than known water base thermosiphon passive cooling systems.
An object of the invention is to provide a passive cooling system utilizing energy storage rods for providing a great amount of cold storage in a small, compact volume.
Another object of the invention is to provide a passive cooling system which utilizes liquid FREON as a heat transfer fluid to cool enclosed heat-producing equipment thereby preventing damage to the equipment from leaking heat transfer fluid, since the FREON will vaporize in the event that it leaks into the enclosure.
Still another object of the invention is to provide a passive cooling system which is maintenance-free.
Yet another object of the invention is to provide an alternative totally integrated passive cooling package which can be installed on top of a roofless heat producing equipment enclosure either in the factory or at the site, rather than forming an integral part of the equipment enclosure.